Phosphor combination and method, particularly adapted for use with explosives, for providing a distinctive information label

ABSTRACT

Phosphor-explosive material combination and method wherein a small amount of inorganic phosphor is mixed with explosive material to provide an indicia or label of information regarding the explosive, either before or after detonation of same. The phosphor can readily be located with an ultraviolet lamp even after the explosive has been detonated, and by correlating the phosphor emission spectra with data known about the explosive when it is manufactured, the explosive can be identified. Line-emitting phosphors are especially useful because of their distinctive emission characteristics, which provide a vast number of possible combinations of emission which are correlated against the data known about the explosive when it is manufactured. Preferably the phosphor is formed as a combination of finely divided &#34;spotter&#34; phosphor and finely divided &#34;coding&#34; material held together by a binder in the form of small conglomerates, in order to facilitate initial location and later identification of same. There exists a vast number of different combinations of distinctive fluorescent emission, and these can be combined to label any item for later identification.

BACKGROUND OF THE INVENTION

This invention generally relates to labeling of an item with anindividualistic and readily identifiable indicia in order to provide anitem identification at a location remote from that location at which thelabel was applied and, more particularly, to a combination explosive andmethod whereby explosive material is coded with information to permit anidentification of the explosive material either before or afterdetonation of same.

The use of commercial explosives is very extensive and a comprehensivesummary and discussion of same is set forth in the Blasters' Handbook,15th. Edition (1969) by E. I. DuPont, Wilmington, Delaware. Accidentalexplosions have always constituted a problem with respect to a properidentification of the explosive involved. In recent years, therelatively large number of terrorists bombings have presentedsubstantial problems, among which is the proper identification of theexplosive used, and the determination of where same might have beenpurchased, etc. Public Law 91-452, Oct. 15, 1970, at 84 Stat. 954requires certain records to be kept for the sale of explosive materials,but once such materials are detonated, it is a most difficult if notimpossible task to trace the distribution of the explosive materialprior to its detonation.

It is also desirable to label items of manufacture or items which aresubjected to handling with an individualistic and readily identifiableindicia in order to provide an item identification at a location remotefrom that location at which the label was applied. One of the problemswith such labeling is that it is extremely difficult to provide a vastnumber of different labels which can be scanned by some type ofautomatic equipment in order to facilitate automatic handling.

It is known in the prior art to apply a fluorescent material to an itemand later trace a possible theft or misappropriation of such items byexposing the hands or garments of a possible suspect to ultravioletradiation, in order to detect the presence of the fluorescent material.Such an indicia, however, normally has merely indicated the presence orlack of such fluorescent material.

In U.S. Pat. No. 3,231,738 dated Jan. 25, 1966, it is suggested to placean organic fluorescent material such as anthracene or fluorescein orrhodamine in a very finely divided state near an explosive charge or thelike so that organic particles will be blown into the air with theexplosion. The airborne path of the particles is then traced by placingsolidified solvent in an open container in the expected path of theparticles, and when the particles fall to earth and strike thesolidified solvent, they can be detected by their fluorescence. All ofthese organic fluorescent materials act as fuels, however, and whenplaced in receptive proximity to the reactive atmospheres and blasteffect resulting from an explosion, these fuels will completely oxidizeor otherwise disintegrate, thereby completely destroying them.

U.S. Pat. No. 3,199,454 dated Aug. 10, 1965 discloses placing an organicfluorescent material such as sodium fluorescein about a small explosivecharge which is to be detonated in water, in order to help controlpredatory fish. The explosive charge is relatively small and thepresence of the water in which the charge is detonated serves to protectthe fluorescein from the blast effects of the detonation so that uponstriking the water, the fluorescein immediately provides an indicativefluorescent response.

It is also generally known to provide tracing or indicative materialsalong with such substances as drugs, and such a technique is disclosedin U.S. Pat. No. 3,341,417 dated Sept. 12, 1967. As described in thispatent, an insoluble radio-opaque substance which is visible underX-rays is included with such drugs as barbiturates, in order that it mayreadly be determined that barbiturates have been ingested.

It is also known to apply organic fluorescent dyes as tracer materialsto commercial items and this is described in U.S. Pat. No. 2,920,202dated Jan. 5, 1960. It should be noted, however, that organicfluorescent materials exhibit an extremely broadband type of fluorescentemission and such dyes are normally used to describe one to twopossibilities, namely, the presence or lack of such dye. A somewhatsimilar use of organic fluorescent dyes is described in U.S. Pat. No.2,392,620, dated Jan. 8, 1946 wherein fluorescent dyes are placed inhydrocarbon products in order to show the presence or lack ofundesirable crude oil in a desired crude oil.

Other uses for fluorescent dyes such as rhodamine are to embed suchmaterials in plastic containers for the purpose of detecting possiblecontamination which may result from abrasion between the packagedcomponent and the packaging film and such a technique is described inU.S. Pat. No. 3,422,265 dated Jan. 14, 1969.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided explosiveagent or explosive material which preferably has a form suitable foruse. Incorporated with the explosive material is a relatively smallamount of inorganic phosphor means which is positioned in receptiveproximity to the shock, pressures, high-temperatures and reactiveatmospheres which result from the detonation of the explosive. Thephosphor survives the explosive blast and can readily be detected byultraviolet light, for example, and the fluorescence of the phosphorcomprises a readily identifiable indicia of information regarding theexplosive. In its preferred form, the phosphor is in a finely dividedstate and along with other finely divided material is retained inintimate association in the form of small conglomerates. The otherfinely divided material, once it has been located, is readilyidentifiable by its line-emission fluorescent response or by othersuitable techniques. The foregoing requires that the particularindividualistic fluorescent emission be correlated with data known aboutthe explosive at the time it is manufactured, such as manufacturer, dateof manufacture, type of explosive, etc., and such data is all readilyavailable. The foregoing technique of utilizing the line-emissions offluorescent materials can be used to label any item with anindividualistic and readily identifiable indicia in order to provide anitem identification at a location which is remote from that location atwhich the label was applied. No specific orientation of such a label isrequired. When utilizing line-emitting phosphors, there are provided avast number of combinations of different emissions which can be readilycorrelated with the data known about the item at the time the phosphorlabel is applied to the item, so that the item can be traced at a laterdate.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be had to thepreferred embodiment, exemplary of the invention, shown in theaccompanying drawings, in which:

FIG. 1 is an elevational view, partly broken away, of an explosivecartridge such as a stick of dynamite, showing phosphor conglomerates ofthe present invention scattered throughout the dynamite;

FIG. 2 is a greatly enlarged view of one of the phosphor conglomeratesof the present invention;

FIG. 3 is a flow chart illustrating the basic method steps which areutilized in coding explosives for later identification;

FIG. 4 is a graph of energy versus wavelength showing the spectraldistribution for a cool white halophosphate phosphor, which can be usedas a spotting phosphor;

FIG. 5 is a graph similar to FIG. 4, but showing the spectral energydistribution for a calcium tungstate phosphor, which can be used as aspotting phosphor;

FIG. 6 is a graph similar to FIG. 4, but showing the spectral energydistribution for a zinc silicate phosphor, which can be used as aspotting phosphor;

FIG. 7 is a graph or relative energy versus wavelength showing theexcitation and emission spectra for trivalent europium-activated yttriumoxide, which can be used as a coding phosphor;

FIG. 8 is a view similar to FIG. 7, but shown for trivelentterbium-activated yttrium oxide;

FIG. 9 is a graph similar to FIG. 7, but taken for a lanthanum oxidehost which is activated by trivalent samarium;

FIG. 10 is a graph similar to FIG. 7, but taken for a trivalentdysprosium-activated phosphor;

FIG. 11 is a graph similar to FIG. 7, but taken for a trivalentgadolinium-activated phosphor;

FIG. 12 is a graph similar to FIG. 7, but taken for a trivalenterbium-activated phosphor;

FIG. 13 is a graph similar to FIG. 7, but taken for a trivalentholmium-activated embodiment;

FIG. 14 is a graph similar to FIG. 7, but taken for a lanthanum oxidehost activated by trivalent praesodymium;

FIG. 15 is a graph similar to FIG. 7, but taken for a lanthanum oxidehost activated by trivalent thulium;

FIG. 16 is a flow chart illustrating the basic steps utilized inlabeling an item for later identification through the use ofline-emitting phosphors;

FIG. 17 is a schematic view of an apparatus which could be utilized forscanning a previously labeled item in order to derive the informationwhich had previously been placed thereon;

FIG. 18 is a plan view of the item shown in FIG. 17, taken along thelines XVIII--XVIII in the direction of the arrows; and

FIG. 19 is an isometric view of an alternative excitation source andmodified filter, as could be used with the scanning apparatus as shownin FIGS. 17 and 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The details for handling and making commercial explosives, includingdynamite, are well known and for further information, reference is madeto the foregoing Blaster's Handbook and to other known literature, suchas U.S. Pat. No. 2,211,737 dated Aug. 13, 1940 and U.S. Pat. No.2,344,149 dated Nov. 9, 1943. In accordance with the present invention,during the manufacture of explosive cartridges, such as a dynamitecartridges, there is incorporated in intimate association with theexplosive material and in immediate and receptive proximity to theshock, pressure, high-temperature and reactive atmospheres resultingfrom the detonation thereof, a small amount of finely divided,particulate, inorganic phosphor means which comprises a readilyidentifiable indicia, as will be explained in detail hereinafter. Thisfluorescence indicia is correlated against then-known predetermined dataregarding the explosive material, for example the manufacturer' indicia,the type of explosive, the year of manufacture, the month ofmanufacture, the week of manufacture, and if desired, even the day ofmanufacture in the case of high volume explosives.

Since the distribution channels for the explosive can be recorded, theindicia which is provided by the phosphor can be correlated against thedistribution of the explosive.

In FIG. 1 is shown a generally conventional dynamite cartridge 20 whichcomprises a fibrous casing 22 enclosing the dynamite 24 having scatteredthroughout small phosphor conglomerates 26, in accordance with thepresent invention. The usual florescent phosphor materials, such as areused in fluorescent lamps, are quite finely divided and a representativeaverage particle diameter is in the order of 6-8 microns. If such veryfinely divided material, such as halophosphate phosphor, were to bescattered throughout the dynamite, the finely divided particles wouldsurvive the detonation and would be detectable at night as viewed under254 nm ultraviolet radiations. They would be quite difficult to pick up,however, because of their extremely small size, and only one indicia ofinformation would be available from any one fluorescent phosphormaterial. While this would be useful, it is highly desirable to providea large amount of readily available information for any particularexplosive.

In accordance with the preferred form of the present invention,fluorescent materials which have very distinctive emissions are utilizedin combination to provide a vast number of different fluorescentemissions which can be readily detected. The most distinctivefluorescent emitting materials are those of the lanthanide series ofrare-earth metals which, apparently because of the incompletely filled4F-shells, possess a large number of sharp levels. The transitionsbetween these provide a many-line spectrum, in contrast to the usualtype of fluorescent materials which usually provide a continuous orso-called band-type emission.

In accordance with the preferred form of the present invention, typicalcommercial phosphors such as are used in fluorescent lamps, for example,are used as what can be termed "spotting" phosphors and there are mixedtherewith a predetermined combination of different line-emitting"coding" phosphors which provide a very individualistic emission whenexcited by predetermined energy such as ultra-violet radiation. Theband-emitting phosphors and line-emitting phosphors are mixed togetherin the form of small conglomerates 26, such as shown in FIG. 2, andthese small conglomerates are dispersed throughout the explosive, suchas the dynamite cartridge. When the explosive material is detonated,there is usually some shattering of the conglomerates, but because ofthe very large number of phosphor particles which are contained in eachconglomerate, the recovered conglomerates, even though shattered, willcontain a representative sampling of all different phosphor particlesused for identification. The individual phosphor coding which iscontained within each conglomerate is therefore readily identifiable, aswill be explained hereinafter.

As a specific example for forming the conglomerate 26 such as shown inFIG. 2, 90 percent by weight of a very finely divided commercial"spotting" phosphor 28, such as apatite structured cool-whitehalophosphate activated by antimony and manganese, is mixed with 10percent by weight of very finely divided "coding" phosphor 30, anexample of which is yttrium oxide activated by trivalent europium. Theforegoing finely divided phoshphor mixture is mixed with an aqueoussolution of potassium silicate (75 percent by weight H₂ O) to form avery thick paste and this paste is spread in a layer approximately twomm thick and permitted to air dry for twelve hours. After air drying,the material is baked at a temperature of approximately 80° C. for aperiod of three hours and then is allowed to cure for about 24 hours.The cured mass comprises about 80 percent by weight phoshphor and 20percent by weight potassium silicate. Thereafter, the resulting hardmass is reduced to a particulate status, such as by grinding or hammermilling. The resulting milled product is then passed over a sieve No. 20and then over a sieve number 40 to separate the fines and coarses. Theresulting conglomerates have a particle size in the order of 0.5 to 0.7mm. Because of the extremely fine state of division of the phosphorparticles, each of the conglomerates 26 as shown in FIG. 2 will normallycontain well in excess of one million individual phosphor particlesbound by the binder 32 so that an extremely large number of differentfinely divided phosphor materials can be mechanically mixed together andeach resulting conglomerate will contain a substantial number ofparticles of each of the different phosphors which are utilized. Theresulting conglomerates 26 are then thoroughly mixed into the explosive,such as dynamite, during its processing into a form suitable for use. Inthe case of cast explosives, the conglomerates can be dispersedthroughout the molten explosive and cast with same. The amount ofphosphor material which is incorporated into the dynamite is in no waycritical and amounts of from 0.01 percent by weight to 1 percent byweight can be utilized. Smaller or larger amounts of phosphor also canbe utilized. In the case of a conglomerate 26 such as shown in FIG. 2,the weight of the conglomerate will be approximately one milligram. If0.1 percent by weight of conglomerates are used with a 200 gram stick ofdynamite, there will be approximately 200 of the conglomerates 26scattered throughout the dynamite stick. Of course, in identifying theinformation which is contained within each conglomerate, it is necessaryto find only one of the conglomerates, or a large residual fragmentthereof, such as by using an ultraviolet light under conditions ordarkness, pick up the conglomerate with a tweezer, and analyze thefluorescent response with a conventional mono-chromator, as will beexplained hereinafter.

The emission spectra of the lanthanide series of rare-earth metals havebeen studied in detail and are set forth in comprehensive form inApplied Physics, Vol. 2, No. 7, July 1963 at page 608. In the followingTable I are set forth the lanthanide rare-earth metals which can beutilized as activators in order to provide very distinctive lineemissions of radiations, along with some other activator ions whichprovide line-appearing type emissions. These activators can be used withmany different host or matrix materials to form a phosphor and, as anexample, yttrium oxide has been found to be a very suitable hostmaterial for many of these metals to provide many different phosphorswhich can be used for coding purposes. These phosphors are all wellknown and the general properties of rare-earth metal activated materialsare described in the Journal of the Electrochemical Society, Volume 111,No. 3, Mar. 1964, at pages 311-317.

                  TABLE I                                                         ______________________________________                                               Pr.sup.+3     Dy.sup.+3                                                       Nd.sup.+3     Ho.sup.+3                                                       Sm.sup.+3     Er.sup.+3                                                       Sm.sup.+2     Tm.sup.+3                                                       Eu.sup.+3     Yb.sup.+3                                                       Cr.sup.+3     V.sup.+3                                                        Gd.sup.+3     Mn.sup.+4                                                       Tb.sup.+3     UO.sub.2.sup.+2                                                 Fe.sup.+3                                                              ______________________________________                                    

The Cr⁺ ³ ions are readily assimilated into an Al₂ O₃ host material. Asuitable host for Mn⁺ ⁴ is magnesium fluorogermanate, and UO₂.sup.⁺² isreadily assimilated into a lithium fluoride host. V⁺ ² is readilyassimilated into a magnesium oxide host, and Fe⁺ ³ into LiAl₅ O₈. Sm⁺ ²is readily assimilated into CaF₂. The trivalent lanthanide rare-earthmetals normally can be used with one or more of an yttrium oxide host,an ytrrium orthovanadate host, a lanthanum phosphate host, or agadolinium vanadate host.

The actual width of a fluorescent line as emitted by a rare-earth metalactivated phosphor is generally in the order of three to ten Angstromsas measured at an intensity which is 50 percent of the maximumfluorecent intensity of the emission. This narrow line of emissionshould be contrasted to the emission of calcium tungstate as shown inFIG. 5, wherein the width of the band, as measured at an emissionintensity which is 50 percent of the maximum intensity, is 1250Angstroms. For the purposes of this invention, a line-emitting phosphoris described as one for which the emission, as viewed through aspectroscope, appears as one or more lines, in contrast to a "band"which occupies a band in the visible spectrum, as viewed with aspectroscope. Of course, the phosphor emission is not restricted to thevisible and may occur in the ultraviolet or infrafed.

To enable the conglomerates 26 to be readily located after an explosivematerial is detonated, it is desirable to incorporate with eachconglomerate a substantial proportion of fluorescent material whichserves primarily as a spotter or locator. Most of the commercialphosphors which are used in fluorecent lamps can be used for suchpurpose and these phosphors normally have a continuous or band-typeemission. Of course, the so-called spotter phosphor could also be usedto provide information and, for example, a different spotter phosphorcan be used to identify each different manufacturer of explosives.

As a specific example, in the following Table II different knowncommercial phosphors are utilized to provide an indicia of themanufacturer of explosives wherein a different spotter phosphor is usedfor each of eight different explosive manufacturers. These phosphors allhave differing band-type emissions and for purposes of illustration, theemission spectrum for a cool white halophosphate is shown in FIG. 4, theemission spectrum for calcium tungstate is shown in FIG. 5, and theemisson spectrum for zinc silicate is shown in FIG. 6.

                  TABLE II.                                                       ______________________________________                                        INDICIA OF MANUFACTURER PROVIDED BY                                           SPOTTER PHOSPHOR                                                              ______________________________________                                        Manufacturer:                                                                              Spotter phosphor                                                 ______________________________________                                        1            Bluish white halophosphate.                                      2            Cool white halo.                                                 3            Warm white halo.                                                 4            Calcium tungstate.                                               5            Zinc silicate-manganese.                                         6            Calcium silicate-manganese.                                      7            Cadmium borate-manganese.                                        8            Strontium magnesium phosphate-tin                                ______________________________________                                    

A band-type emitting phosphor can also be used, if desired, to providesupplemental information such as an indicia of permissible ornon-permissible explosives, as designated by the Bureau of Mines. As anexample, magnesium tungstate phosphor could be included in small amountto provide an indicia of permissible explosive and manganese-activatedcalcium gallate could be utilized to provide an indicia ofnon-permissible explosive. The number of phosphors which could besubstituted for the foregoing specific examples are numerous and forfurther examples, reference is made to Leverenz, Luminescence of Solids,published by Wiley and Sons, New York (1950) see Table V following page72 of this reference. As a general rule, phosphors which will oxidizereadily desirably should be avoided.

There are numerous different types of dynamites and the foregoingBlaster's Handbook indicates that there are eighteen differentcommercial types. In addition to the many different types of dynamite,there are also many other types of explosives, such as ammonium nitrate,TNT, etc. In the following Table III, five different

                                      TABLE III.                                  __________________________________________________________________________    CODING FOR TYPE OF EXPLOSIVE                                                  __________________________________________________________________________    Type of dynamite                                                                         1 2 3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18                __________________________________________________________________________    Coding    Pr Nd                                                                              Sm Eu Gd Pr Pr Pr Pr Nd Nd Nd Sm Sm Eu Pr Pr Pr                                        Nd Sm Eu Gd Sm Eu Gd Eu Gd Gd Nd Nd Nd                                                                      Sm Eu Gd                Type of other                                                                 explosive e.g.                                                                NH.sub.4 NO.sub.3 TNT, etc.                                                                           19 20 21 22 23 24 25 26 27 28 29 30 31                                        Pr Pr Pr Nd Nd Nd Sm Pr Pr Pr Pr Nd Pr                Coding                  Sm Sm Eu Sm Sm Eu Eu Nd Nd Nd Sm Sm Nd                                        Eu Gd Gd Eu Gd Gd Gd Sm Sm Eu Eu Eu Sm                                                             Eu Gd Gd Gd Gd Eu                                                                            Gd                __________________________________________________________________________     Note. All of the foregoing activator metals are trivalent.   phosphors        which are activated by different rare-earth metals are utilized to provide     a code comprising thirty-one different combinations or "words", namely, a     different "word" for each of the eighteen types of dynamites and thirteen     remaining "words" which can be used to designate other types of     explosives.

To designate a code for the year of manufacture, three phosphorsactivated by different rare-earth metals are utilized as set forth inthe following Table IV. This is set up for a seven year repeating basis.

                  TABLE IV                                                        ______________________________________                                        Coding for Year of Manufacture                                                ______________________________________                                        Year of Mnfg.                                                                           71     72     73   74   75    76    77                                        Tb     Dy     Ho   Tb   Tb    Dy    Tb                              Coding                       Dy   Ho    Ho    Dy                                                                            Ho                              ______________________________________                                    

To designate different codings for the month of manufacture, fourdifferent phosphors activated by different rare-earth metals are listedin the following Table V and in Table VI, other line-emitting activatorions are used to designate the week of manufacture.

                                      TABLE V                                     __________________________________________________________________________    CODING FOR MONTH OF MANUFACTURE                                               __________________________________________________________________________    Month of mgf                                                                             1  2 3  4 5  6  7  8  9 10 11 12                                   __________________________________________________________________________               Sm Er                                                                              Tm Yb                                                                              Sm Sm Sm Er Er                                                                              Tm Sm Sm                                   Coding               Er Tm Yb Tm Yb                                                                              Yb Er Tm                                                                         Tm Yb                                   __________________________________________________________________________     Note.-Sm is 2+-all other are 3+.                                         

                  TABLE VI                                                        ______________________________________                                        CODING FOR WEEK OF MANUFACTURE                                                ______________________________________                                        Week of mnfg                                                                              1       2       3     4     5                                     ______________________________________                                                        Cr.sup.+3                                                                             Mn.sup.+ 4                                                                          UO.sub.2.sup.+3                                                                     Cr.sup.+3                                                                           Cr.sup.+3                           Coding                              Mn.sup.+4                                                                           UO.sub.2.sup.+2                     ______________________________________                                    

Referring again to Table I, the various different phosphors which allemit distinctive line emissions provide 2¹⁷ or over 131,000 differentposibilities. If 10 different spotters are utilized, and this number canbe greatly increased if desired, the number of possible combinationssubstantially exceeds one million. For the purposes of codingexplosives, this is thought to be adequate although the number could begreatly expanded by utilizing different identification techniques ifdesired, as will be explained hereinafter.

As a specific example, if manufacturer number 4, as set forth in TableII, were to manufacture a certain type of dynamite, he would incorporatetherein the phosphor conglomerates which were formed of calciumtungstate as a spotter phosphor, magnesium tungstate as an indicia orpermissible explosive, praseodymium-activated ytrrium oxide which couldbe used as a code for straight dynamite (See Table III),terbium-activated yttrium oxide which would indicate 1971 as the year ofmanufacture (see Table IV), erbium-activated yttrium oxide which wouldindicate February as the month of manufacture (see Table V) and chromiumactivated Al₂ O₃ which would indicate the first week of manufacture (seeTable VI). As an example, the finely divided phosphor materials would bemixed in the proportion of 80 percent by weight calcium tungstate, 10percent by weight magnesium tungstate, and 2 percent by weight of eachof the five remaining coding constituents. Since each conglomerate ofphosphor contains well in excess of a million individual phosphorparticles, each conglomerate is assured of having a representativesampling of each of the spotting and coding constituents which areutilized. After the blast under investigation has occurred, theinvestigators would wait until dark and them systematically irradiatethe area of the blast with 254 nm ultraviolet radiations to which thespotter phorpher responds with a bright blue fluorescence. Once anindividual conglomerate or large residual fragment thereof is located,it is a simple matter to pick it up with a tweezer, and analyze sameunder a monochromator to detect the manufacturer and the characteristicline emissions, which would then be correlated back to the manufacturersrecords. Since the manufacturer keeps the statistics on the distributionof the dynamite, this will provide an indicia of the source, type anddistribution of the explosive.

For purposes of illustration, the principal emission lines and theexcitation spectra for various rare-earth metal activated phosphors areillustrated in FIGS. 8 through 15. The emission lines as shown are onlythe primary lines and in most cases, the line emissions of theserare-earth metals are much more complex.

In the foregoing examples, it is possible to accommodate two or morerare-earth metals as activator materials into the same host or matrixand as many as four can be readily accommodated. In view of the largenumber of particles which are present in each conglomerate, however, itis probably just as simple to utilize one rare-earth metal or otherline-emitting activating ion in each host.

In analyzing the located conglomerates for emisson spectrum, thephosphor can be irradiated with energy which will excite the host, whichenergy is then transferred to the activators which providecharacteristic emission. As a second method, each rare-earth ion can beexcited directly by using a tunable excitation source whose outputwavelength is scanned over the wavelengths containing the sharpabsorption lines of the various activators. The resulting fluorescenceis monitored to determine the variation of fluorescent energy withexcitation wavelength. As an example, if the host is yttrium oxideactivated with europium and terbium, excitation peaks at 395.5 nm foreuropium and 309 nm for terbium are easily seen by monitoring thefluorescent output in the wavelength range of from 500-700 nm, whichcontains many of the fluorescent lines of the europium and terbium ions.As an alernative method for observing the spectrum of the locatedphosphor conglomerate, the presence or absence of europium is determinedby exciting the conglomerate with a wavelength of 395.5 nm and observingthe presence or absence of the europium fluorescent line at 611.2 nm.Correspondingly, the presence or absence of terbium is noted if anexcitation at 309 nm produces, or fails to produce, a fluorescentemission line at 543 nm. The detection of the presence or absence of avery minute quantity of phosphor is extremely accurate using theforegoing techniques.

The conglomerates need not use line-emitting fluorescent phosphors as"coding" indicia, but could readily use other forms of identifyingindicia, provided such material could be located after a blast.Relatively simple techniques for identification are those of emissionspectroscopy or X-ray fluorescence. The technique of atomic absorptionspectroscopy is also well known and can be used to detect very minutequantities of various elements and this is described in the book byRobinson entitled "Atomic Absorption Spectroscopy" published by Dekker,New York (1966). In the foregoing Table VII are listed some elementswhich are suitable for detection utilizing this atomic absorptionspectroscopy technique. These elements should be mixed in a stable form,such as the oxides, phosphates or silicates, for example, as very finelydivided material comprising a part of the conglomerate 26 as shown inFIG. 2.

                  TABLE VII                                                       ______________________________________                                                 Li            Ni                                                              K             Cu                                                              Rb            Ag                                                              Cs            Au                                                              Sr            Zn                                                              Cr            Cd                                                              Mn            Sb                                                              Co            Te                                                                            Bi                                                     ______________________________________                                    

Many other techniques are available for identifying particular materialsonce they have been located such as the procedure described in the bookentitled "Neutron Irradiation and Activation Analysis" by Taylorpublished by Newnes, London, (1964). Elements which can readily bedetected utilizing such neutron irradiation and activation analysistechnique are set forth in the following Table VII. An notedhereinbelow, these elements should be present as stable compounds.

                  TABLE VIII                                                      ______________________________________                                        Eu               Cu          Yb                                               Dy               Ga          Cd                                               Ho               Au          Co                                               In               La          Mn                                               Ir               Pd          Sb                                               Lu               Sm          Sc                                               Re               Pr          Ta                                               As               Gd          W                                                Tb               Zn          P                                                Er                                                                            Y                                                                             ______________________________________                                    

The listed elements need only be present in extremely minute quantity inorder to be detected and these techniques could be used to supplementthe foregoing emission spectra analysis technique which has beendescribed in detail. Combining all the possibilities which result fromthese added techniques, there is indeed a vast number of possiblecombinations of coding which could be used.

As noted hereinbefore, while a single inorganic phosphor placed into anexplosive in very finely divided form will provide one indicia ofinformation, it is preferred to incorporate many different phosphorsinto small phosphor conglomerates so that a large number of bits ofinformation will be contained in each conglomerate. In addition, thevery size of the conglomerate also facilitates their being readilysegregated from the debris of the explosion. The inorganic bindermaterial which is used should be transmissive of at least that energywhich excites the spotter phosphor and it should be transmissive of theradiation which the spotter phosphor produces when excited. In the usualcase, the phosphor will be responsive to either short wavelength or longwavelength ultraviolet radiations, although other forms of phosphorexcitation could be used if desired.

The foregoing specific example has considered potassium silicate as aphosphor binder which meets the foregoing requirements. Many otherinorganic binders could be utilized such as sodium silicates which rangein composition from Na₂ O.sup.. 2SiO₂ to Na₂ O.sup.. 4SiO₂. Thesesilicates air dry to hard films which do not readily dissolve and ifthey are heated, the binders will freeze into a solid foam typematerial. With respect to the potassium silicates, the compositionsrange from K₂ O.sup.. 3.9SiO₂ to K₂ O.sup.. 3.3SiO₂. Glass-forminginorganic materials can also be used as binders and these include thewell known soda-lime-silica glasses of which there are numerousdifferent compositions. Glass-ceramic compositions, which are wellknown, can also be used as binders. Other refractory materials could beused as a binder fabricated about the phosphor particle with a sinteringtype of process. As a general rule, it has been found that the finer thephosphor particles, the stronger the particle conglomerate with respectto resisting the blast effects of the detonation. With most phosphormaterials, it is a relatively simple matter to obtain ultimate particleswhich have a diameter in the order of two microns and less.

When the explosive material is detonated, there may be some fracturingof the individual conglomerate, but the continuity of the conglomeratesis sufficiently maintained that each conglomerate will contain allcoding information which is initially placed therein. The conglomeratescan even be intermixed with RDX and, after detonation, the continuity ofthe conglomerates will still be preserved to a degree sufficient toinsure that all coding information is present. This is about as extremea test as the conglomerates can be subjected to, because of theextremely high velocity of detonation and high detonation pressures ofthis explosive material.

The line-emitting phosphors can be applied as separate patches to labelany item with an individualistic and readily identifiable indicia toprovide an item identification at a location which is remote from thatlocation at which the label was applied. No specific orientation of thelabel is required. In practicing such a method, as is generally shown inthe flow chart of FIG. 16, there is first assembled a combination ofdifferent phosphor materials at least the substantial portion of whichare inorganic phosphors activated by different ions which taken togetherprovide a vast number of different known combination of distinctive lineemissions when the phosphors are excited by predetermined energy otherthan visible light. The known phosphor combination is then secured inintimate association, as a label for example, with the item to beidentified. Thereafter, when it is desired to identify the item, theknown combination of line emissions is correlated against the previouslyrecorded combination of emissions so that the item is readilyidentified. Turning to the number of ions which will provide lineemitting phosphors as disclosed in Table I, the number of differentcombinations disclosed in this table alone exceed 131,000. In FIGS. 17and 18 are shown an example of a coded item 34 wherein each of the fourpatches 36, 38, 40 and 42 comprise a different rare-earth metalactivated phosphor to comprise a coded label, 44. The labeled item 34 ispassed on a conveyor belt 46 beneath an ultraviolet lamp 48 and thefluorescence of the label 44 is scanned by a pick-up photocell 50 orsimilar conventional read-out device.

The foregoing number of possible combinations can be extendedsubstantially by using each line-emitting activator ion in two or moredifferent hosts which have what the phosphor art terms larger band gapenergies, with each host being capable of transferring energy to theline-emitter activator ion. In decoding the information, the phosphorswould be excited sequentially with two or more wavelengths of light ofprogressively shorter wavelength. The first exciting longer wavelengthwould be capable of exciting only that host which had the lowest bandgap energy, the next shorter wavelength would be capable of exciting thesecond host, and so forth. As a specific example, yttrium oxide (Y₂ O₃)has a band gap energy of 5.8 ev; the host Y₂ O₂ S has a band gap energyless than 5.8 ev; the host Y₂ OS₂ has a band gap energy substantiallyless than 5.8 ev and greater than 2.5 ev; and the host Y₂ S₃ has a bandgap energy of about 2.5 ev. All of these hosts would be activated by atrivalent europium, for example, and they would be sequentially excitedfirst with long wavelength energy and then with progressively shorterwavelength energy with the resulting fluorescence observed. For example,the label would be pumped sequentially with wavelengths of 3 ev, 4 ev, 5ev and 6 ev. In this manner, the total number of possible combinationscould be extended substantially.

As a second possibility of decoding the combination of line-emitters, aplurality of hosts which have progressively larger band gap energieswould be utilized as in the previous example and these would be excitedsequentially with successively higher energies (i.e., shorter wavelengthexcitations). Between the excitation source 48 and the fluorescent label44 would be placed a set of filters, each of which is capable of passingone and only one of the exciting energies. For purposes of illustration,one filter 52 is shown in FIG. 17. This would greatly extend the numberof total combinations. The use of more than one filter 52 will normallyrequire a separate ultraviolet lamp 48. This technique could also beused to eliminate spurious emissions as might occur from a fluorescentdye actually incorporated as a part of an item to be detected. Thefluorecent dye would in all probability respond to all energies and bydeliberately omitting from the label a phosphor which will respond to apredetermined excitation energy, the possibility of spurious signalscould be eliminated since if the labeled item did respond to apredetermined excitation, the presence of the fluorescent dye would beindicated. As an example, if an excitation energy of 300 nm were used toexcite a fluorescent dye such as sodium fluorescein, and no phosphorwere present which would respond to such excitation, the presence of thefluorescent dye would be indicated, and the item would have to bespecially handled.

In FIG. 19 is shown a modified form of excitation source 48a, which forthis embodiment is a reflector-type high-pressure mercury vapor lamp,modified to incorporate an ultraviolet transmitting faceplate. This lampemits strong radiations at 254 nm and 365 nm. Between the lamp 48a andthe object to be irradiated, such as the label 44 as shown in FIG. 17,is placed a rotating filter 52a, one half portion 54 of which is afilter which passes only 254 nm radiations and the other half portion 56of which passes only 365 nm radiations. In this manner, the label 44 canbe sequentially excited with successively varying energies as the filter52a is rotated. The signal from the photocell 50 is read only when theitems which comprise the label 44 are irradiated only with the 254 nmexcitation or the 365 nm excitation.

As an alternative embodiment, the small conglomerates can be coated witha non-fluorescing, ultraviolet-radiation-absorbing organic combustible,such as polymethyl methacrylate. If the explosive cartridge is brokenopen and exposed to ultraviolet radiations, the coated conglomerateswill not fluoresce and their detection and removal will be a mostdifficult task. When the explosive cartridge is detonated, however, theorganic coating will burn in the reactive atmospheres, leaving theresidual fluorescent conglomerates. Such a coating may also have benefitin forming a seal about the conglomerates to inhibit absorption of anymaterial of the environment in which the conglomerates are intended tobe used.

While the foregoing description has been generally directed to coding ofcommercial-type explosives, the techniques described herein could alsobe used to code other types of explosives and propellant materials. Thecoding techniques as described can also be used to identify explosiveagents. As an example, ammonium nitrate could be coded with the phosphorconglomerates. When this explosive agent is further processed into aform suitable for use, the conglomerates would remain in the resultingexplosive material.

We claim as our invention:
 1. In combination, explosive agent orexplosive material and associated means which will provide an indicia ofinformation regarding said explosive agent or explosive material, saidcombination comprising:a. an explosive agent or explosive material; andb. a relatively small amount of inorganic phosphor means incorporatedwith and retained in intimate association with said explosive agent orexplosive material and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily identifiable indicia of information regarding saidexplosive agent or explosive material.
 2. In combination, solidexplosive material and associated individualistic and readilydeterminable phosphor means which will provide an indicia of informationregarding said explosive material either before or after detonation ofsame, said combination comprising:a. solid explosive material; and b. arelatively small amount of conglomerated small particles scatteredwithin said explosive, said conglomerated particles comprising a firstfinely divided phosphor material which is excited by predeterminedenergy to produce a predetermined emission of readily detectableradiations, at least one finely divided second phosphor material whichis excited by predetermined energy to produce a predeterminedindividualistic emission of radiations which is different from theemission of said first phosphor material, and inorganic binder materialintimately holding together said first phosphor material and secondphosphor material as a plurality of small particles each comprising saidconglomerates of said first finely divided phosphor material and saidsecond finely divided phosphor material, and said binder materialtransmissive of at least said predetermined energy which excites saidfirst phosphor material and transmissive of said readily detectableradiations produced by said excited first phosphor material.
 3. Thecombination as specified in claim 2, wherein said explosive materialcomprises dynamite, said first phosphor material is efficiently excitedby ultra-violet radiations to provide a band-type emission, said secondphosphor material is excited by ultra-violet radiations to produce aline-type emission, and the relative amount of said first phosphormaterial substantially exceeds the relative amount of said secondphosphor material.
 4. The combination as specified in claim 3, whereinsaid conglomerates comprise from about 0.01 to 1 percent by weight ofsaid dynamite, said conglomerates are of such size as to weigh about onemilligram each, said first and second phosphor materials comprise about80 percent by weight of said conglomerates, said first phosphor materialis apatite structured halophosphate activated by antimony and manganese,and said second phosphor material comprises yttrium oxide matrixactivated by trivalent europium, and the weight ratio of said firstphosphor material to said second phosphor material is about 90:10. 5.The combination as specified in claim 2, wherein said solid explosivematerial has the general configuration of an explosive cartridge.
 6. Incombination, an explosive cartridge and associated means which willprovide an indicia of information regarding said explosive cartridge,said combination comprising:a. an explosive cartridge comprising acasing and explosive material enclosed by said casing; and b. arelatively small amount of inorganic fluorescent phosphor meansincorporated with and retained in intimate association with saidexplosive cartridge and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily locatable indicia of information regarding saidexplosive cartridge.
 7. In combination, explosive agent or explosivematerial and associated means which will provide an indicia ofinformation regarding said explosive agent or explosive material, saidcombination comprising:a. an explosive agent or explosive material; andb. a relatively small amount of inorganic phosphor means incorporatedwith and retained in intimate association with said explosive agent orexplosive material and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily identifiable indicia of information regarding saidexplosive agent or explosive material, said phosphor means is in finelydivided form, and finely divided other material is retained in intimateassociation with said phosphor means in the form of small conglomerates,said finely divided other material upon identification providingindividualistic indicia of information, and once said other material hasbeen located, said other material is readily identifiable.
 8. Incombination, explosive agent or explosive material and associated meanswhich will provide an indicia of information regarding said explosiveagent or explosive material, said combination comprising:a. an explosiveagent or explosive material; and b. a relatively small amount ofinorganic phosphor means incorporated with and retained in intimateassociation with said explosive agent or explosive material andreceptive to the shock, pressure, high temperature and reactiveatmospheres resulting from the ultimate detonation thereof, and thefluorescence of said phosphor means comprising a readily identifiableindicia of information regarding said explosive agent or explosivematerial, said phosphor means is in finely divided form, and finelydivided other material is retained in intimate association with saidphosphor means in the form of small conglomerates, said finely dividedother material upon identification providing individualistic indicia ofinformation, and once said other material has been located, said othermaterial is readily identifiable by at least one of the procedures ofemission spectroscopy, atomic absorption spectroscopy, X-rayfluorescence analysis, neutron irradiation and activation analysis, ordistinctive fluorescent emission response.
 9. The combination asspecified in claim 8, wherein said conglomerates are scatteredthroughout said explosive agent or explosive material.
 10. Incombination, explosive agent or explosive material and associated meanswhich will provide an indicia of information regarding said explosiveagent or explosive material, said combination comprising:a. an explosiveagent or explosive material; and b. a relatively small amount ofinorganic phosphor means incorporated with and retained in intimateassociation with said explosive agent or explosive material andreceptive to the shock, pressure, high temperature and reactiveatmospheres resulting from the ultimate detonation thereof, and thefluorescence of said phosphor means comprising a readily identifiableindicia of information regarding said explosive agent or explosivematerial, said phosphor means is in finely divided form, and finelydivided other material is retained in intimate association with saidphosphor means in the form of small conglomerates, said finely dividedother material upon identification providing individualistic indicia ofinformation, and once said other material has been located, said othermaterial is readily identifiable by at least one of the procedures ofemission spectroscopy, atomic absorption spectroscopy, X-rayfluorescence analysis, neutron irradiation and activation analysis, ordistinctive fluorescent emission response, and said distinctivefluorescent emission response comprises line emisson fluorescentresponse.
 11. In combination, an explosive cartridge and associatedmeans which will provide an indicia of information regarding saidexplosive cartridge, said combination comprising:a. an explosivecartridge comprising a casing and explosive material enclosed by saidcasing; and b. a relatively small amount of inorganic fluorescentphosphor means incorporated with and retained in intimate associationwith said explosive cartridge and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily located indicia of information regarding saidexplosive cartridge, said phosphor means is in finely divided form, andfinely divided other material is retained in intimate association withsaid phosphor means in the form of small conglomerates, said finelydivided other material upon identification providing individualisticindicia of information, and once said other material has been located,said other material is readily identifiable.
 12. In combination, anexplosive cartridge and associated means which will provide an indiciaof information regarding said explosive cartridge, said combinationcomprising:a. an explosive cartridge comprising a casing and explosivematerial enclosed by said casing; and b. a relatively small amount ofinorganic fluorescent phosphor means incorporated with and retained inintimate association with said explosive cartridge and receptive to theshock, pressure, high temperature and reactive atmospheres resultingfrom the ultimate detonation thereof, and the fluorescence of saidphosphor means comprising a readily locatable indicia of informationregarding said explosive cartridge, said phosphor means is in finelydivided form, and finely divided other material is retained in intimateassociation with said phosphor means in the form of small conglomerates,said finely divided other material upon identification providingindividualistic indicia of information, and once said other material hasbeen located, said other material is readily identifiable by at leastone of the procedures of emission spectroscopy, atomic absorptionspectroscopy, X-ray fluorescence analysis, neutron irradiation andactivation analysis, or distinctive fluorescent emission response. 13.In combination, .[.en.]. .Iadd.an .Iaddend.explosive cartridge andassociated means which will provide an indicia of information regardingsaid explosive cartridge, said combination comprising:a. an explosivecartridge comprising a casing and explosive material enclosed by saidcasing; and b. a relatively small amount of inorganic fluorescentphosphor means incorporated with and retained in intimate associationwith said explosive cartridge and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily locatable indicia of information regarding saidexplosive cartridge, said phosphor means is in finely divided form, andfinely divided other material is retained in intimate association withsaid phosphor means in the form of small conglomerates, said finelydivided other material upon identification providing individualisticindicia of information, and once said other material has been locatedsaid other material is readily identifiable by at least one of theprocedures of emission spectroscopy, atomic absorption spectroscopy,X-ray fluorescence analysis, neutron irradiation and activationanalysis, or distinctive fluorescent emission response, and saiddistinctive fluorescent emission response comprises line emissionfluorescent response.
 14. In combination, an explosive cartridge andasscociated means which will provide an indicia of information regardingsaid explosive cartridge, said combination comprising:a. an explosivecartridge comprising a casing and explosive material enclosed by saidcasing; and b. a relatively small amount of inorganic fluorescentphosphor means incorporated with and retained in intimate associationwith said explosive cartridge and receptive to the shock, pressure, hightemperature and reactive atmospheres resulting from the ultimatedetonation thereof, and the fluorescence of said phosphor meanscomprising a readily locatable indicia of information regarding saidexplosive cartridge, said inorganic phosphor means comprises a pluralityof conglomerated small particles, said conglomerated small particlescomprising a first finely divided phosphor material which is excited bypredetermined energy to produce a predetermined emission of readilydetectable radiations, at least one finely divided second phosphormaterial which is excited by predetermined energy to produce apredetermined individualistic emission of radiations which is differentfrom the emission of said first phosphor material, and inorganic bindermaterial intimately holding together said first phosphor material andsecond phosphor material as a plurality of small particles eachcomprising said conglomerates of said first finely divided phosphormaterial and said second finely divided phosphor material, and saidbinder material transmissive of at least said predetermined energy whichexcites said first phosphor material and transmissive of said readilydetectable radiations produced by said excited first phosphor material..Iadd.
 15. An explosive device comprising an explosive material andinorganic luminscent material making-up less than about 1 percent byweight of the explosive device such that prior to detonation of theexplosive device the luminescent material is not readily detectableunder ambient light while following detonation of the explosive devicethe luminescent material is detectable upon excitation by a nonvisibleexcitation radiation. .Iaddend..Iadd.
 16. An explosive device of claim15 in which the luminescent material is present in an amount of fromabout 0.01 to about 1 percent. .Iaddend..Iadd.
 17. An explosive deviceof claim 15 in which the luminescent material is added to explosivematerial in the explosive device. .Iaddend..Iadd.
 18. An explosivedevice of claim 15 in which the luminescent material is a fluorescentmaterial. .Iaddend..Iadd.
 19. An explosive device of claim 15 in whichthe luminescent material is a phosphorescent material. .Iaddend..Iadd.20. An explosive device of claim 15 in which at least two luminescentmaterials are employed. .Iaddend..Iadd.
 21. An explosive device asclaimed in claim 15 in which the average particle size of theluminescent material is about 500 to 700 microns. .Iaddend.